(CustomReceiver).AfterParse

Description

AfterParse is called immediately after your custom receiver is instantiated by
the xml config parser. So, if you need to do any startup logic after config parsing,
like opening file or allocating any resources after the receiver is instantiated, do it here.

If this func returns a non-nil error, then the loading procedure will fail. E.g.
if you are loading a seelog xml config, the parser would not finish the loading
procedure and inform about an error like with any other config error.

If your custom logger needs some configuration, you can use custom attributes in
your config. Check CustomReceiverInitArgs.XmlCustomAttrs comments.

IMPORTANT: This func is NOT called when the LoggerFromCustomReceiver func is used
to create seelog proxy logger using the custom receiver. This func is only called when
receiver is instantiated from a config.